es506065d_si_001.pdf (504.49 kB)
Impacts of Organic Ligands on Forsterite Reactivity in Supercritical CO2 Fluids
journal contribution
posted on 2015-04-07, 00:00 authored by Quin R. S. Miller, John P. Kaszuba, Herbert T. Schaef, Mark E. Bowden, Bernard P. McGrailSubsurface
injection of CO2 for enhanced hydrocarbon
recovery, hydraulic fracturing of unconventional reservoirs, and geologic
carbon sequestration produces a complex geochemical setting in which
CO2-dominated fluids containing dissolved water and organic
compounds interact with rocks and minerals. The details of these reactions
are relatively unknown and benefit from additional experimentally
derived data. In this study, we utilized an in situ X-ray diffraction
technique to examine the carbonation reactions of forsterite (Mg2SiO4) during exposure to supercritical CO2 (scCO2) that had been equilibrated with aqueous solutions
of acetate, oxalate, malonate, or citrate at 50 °C and 90 bar.
The organics affected the relative abundances of the crystalline reaction
products, nesquehonite (MgCO3·3H2O) and
magnesite (MgCO3), likely due to enhanced dehydration of
the Mg2+ cations by the organic ligands. These results
also indicate that the scCO2 solvated and transported the
organic ligands to the forsterite surface. This phenomenon has profound
implications for mineral transformations and mass transfer in the
upper crust.